Modern technologies are developing prosperously. Novel information products are introduced daily for satisfying people's various needs. Early displays are mainly cathode ray tubes (CRTs). Owing to their huge size, heavy power consumption, and radiation hazardous to the heath of long-term users, traditional CRTs are gradually replaced by liquid crystal displays (LCDs). LCDs have the advantages of small size, low radiation, and low power consumption, and thus becoming the mainstream in the market.
LCDs control the transmittance of liquid crystal cells according to data signals for displaying images. FIG. 1 shows a schematic diagram of the display panel and its plurality of pixel structures according to the prior art. As shown in FIG. 1, the display panel comprises a plurality of pixel structures 10′ and a driving chip 20′. The driving chip 20′ produces a driving signal for driving the plurality of pixel structures 10′. Where each of the pixel structures 10′ includes a thin film transistor (TFT) 12′ and a storage capacitor 14′. The gate of the TFT 12′ is coupled to a scan line; the source of the TFT 12′ is coupled to the driving chip 20′; and the drain of the TFT 12′ is coupled to the storage capacitor 14′. Because an active-matrix LCD adopts active switching devices, it is advantageous in displaying moving pictures. TFTs 12′ are mainly used as the switching devices in active-matrix LCDs.
In addition, the applications of TFT LCDs are extensive. Their driving method is to turn on the internal cell using the gate. Then the source is used for supplying the accurate voltage for controlling the orientation of the liquid crystal in the display panel for displaying images. FIG. 2 shows a schematic diagram of the plurality of pixel structures of the display panel and FIG. 3 shows waveform of the driving signal for the plurality of pixel structures according to the prior art. As shown in the figures, the driving chip 20′ will produce a plurality of scan signals G0, G1, . . . , Gn and transmit the plurality of scan signals G0, G1, . . . , Gn sequentially to a plurality of scan lines Ga1, Ga2, . . . , Gan of the plurality of pixel structures. As any of the scan lines is activated, namely, the scan signal reaching VGH, a plurality of data lines S0, S1, . . . , Sn supply the corresponding voltages of image data to the pixel structures 10′ of the display panel and thus displaying the image.
There exists a parasitic capacitor 16′ between the TFT 14′ of the plurality of pixel structures 10′ and the storage capacitor 14′ such as Cs1, Cs2, Cs3, and Cs4 in FIG. 2. Thereby, when the scan signal G0 is cut off, the storage voltages across the storage capacitors Cs1, Cs2 will be shifted downwards by a shift voltage Vsft owing to the parasitic capacitors 16′, which is approximately 1 volt. The driving chip 20′ will provide a reference voltage DC to a common electrode 18′ of the plurality of pixel structures according to the shift voltage Vsft, which is used as a common voltage. Hence, when the scan signal G0 is cut off and the storage voltages across the storage capacitors Cs1, Cs2 are shifted by a shift voltage Vsft owing to the parasitic capacitors 16′, the storage voltages across the storage capacitors Cs 1, Cs2 are still symmetrical to the common voltage of the common electrode 18′ while displaying identical grayscale.
Nonetheless, the parasitic capacitors 16′ vary over the display panel. As the storage voltages across the storage capacitors Cs1, Cs2 are shifted by a shift voltage Vsft, the shift voltage Vsft will be slightly different. Thereby, while displaying identical grayscale, the storage voltages across the storage capacitors Cs1, Cs2 are not symmetrical to the common voltage of the common electrode 18′ and thus producing the flash phenomenon. For overcoming this problem, according to the prior art, the driving chip 20′ needs to provide the reference voltage DC to a common electrode 18′ of the plurality of pixel structures, as shown in FIG. 4, and the voltage tuning function, which will lead to increases in circuit area and power consumption.
Moreover, as the scan signal G0 switches TFTs, as shown in FIG. 5, the voltage level of the common voltage on the common electrode of the pixel structures are influenced, which further influences the displaying quality. Besides, because the plurality of pixel structures of the display panel is not grounded directly, when the panel is influenced by electrostatic charges, the charges have to be released through the contact with the common electrode and via the electrode static discharge circuit 30′, as shown in FIG. 6. Consequently, the electrostatic charges are not released to the ground directly; the electrostatic charges still have the possibility of damaging the circuitry of the driving chip 20′ via the common electrode. Thereby, the endurance of the display panel module according to the prior art to electrostatic charges are inferior.
Accordingly, the present invention provides a novel display panel and the driving circuit thereof for avoiding an extra reference voltage to a common electrode of the plurality of pixel structures and thus reducing circuit area and power consumption. In addition, the displaying quality can be enhanced by eliminating the influence of the switching of scan signal on the common electrode. Furthermore, the endurance of the display panel on electrostatic charges can be improved as well. Thereby, the problems described can be solved.